Transducers for internal combustion engines are used to determine oil pressure and to produce a corresponding indicator signal. Previous transducer designs include diaphragm means, one side of which is exposed to pressurized lubricating oil. In addition to determining oil pressures, there is a need to provide a switch mechanism in the transducer to control an electric fuel pump energization. When starting an engine, the fuel pump motor should be activated only after production of a minimum oil pressure.
A number of U.S. patents disclose a pressure transducer and switch mechanism, either alone or in combination. For example, U.S. Pat. No. 3,321,594 to Reise discloses a fluid pressure actuated switch with a diaphragm sensor operatively associated with electrical contacts to control activation of an electric fuel pump motor. The U.S. Pat. No. 4,255,630 to Hire also discloses an electrical switch which is responsive to fluid pressure to control a fuel pump motor. The U.S. Pat. No. 4,524,255 to Haag discloses a switch with a movable diaphragm responsive to fluid pressure to open and close contacts of an electrical circuit.
The U.S. Pat. No. 4,581,941 to Obermann discloses a fluid pressure transducer including a switch therein adapted to control a fuel pump motor.
Several other patents have been uncovered which disclose pressure transducers without a switching device. These include U.S. Pat. Nos. 3,504,324; 4,449,112; and 4,452,202. All of the patents discussed or identified heretofore broadly disclose a pressure transducer with or without a switching mechanism but do not specifically disclose the desirable design features of the subject transducer with access means to allow calibration after final assembly of the transducer as described hereinafter.